1. Field of the Invention
This invention relates to an analogue, scanning or measurement probe used on a coordinate positioning machine such as a coordinate measuring machine or machine tool, to measure the position or contour of a surface.
Coordinate positioning machines are known to include an arm supported for movement in mutually perpendicular directions relative to a table on which a workpiece is supportable, and transducers for measuring the position of the arm relative to a reference position or datum on the table. A probe typically comprises a fixed structure such as a housing, a stylus supported on a support assembly for 3-dimensional movement relative to the fixed structure, and transducers for measuring the position of the stylus relative to a reference position on the fixed structure.
In use the fixed structure of the probe is secured to the arm of the machine and, in a typical operation, the arm is moved to a predetermined position in which the stylus engages a point on the workpiece where, as a result it is displaced relative to the fixed structure. The sum of the outputs of the respective transducers defines the position of the stylus relative to the datum.
The present invention relates to the type of transducers employed in an analogue probe.
2. Description of Related Art
It is known from U.S. Pat. No. 4,084,323 to provide an analogue probe having a stylus supported relative to a fixed structure by three serially connected parallel springs. Displacement of the stylus relative to the fixed structure is transduced by means of three proximity sensors, mounted on the fixed structure in register with three faces of a cubic iron mass which is mounted to the stylus.